178 WATER REPTILES OF THE PAST AND PRESENT 



more recent discoveries, to belong to a different line of descent and 



has been described under the Protorosauria. 



In the direct line of ancestry there is no known form that was 



distinctly aquatic. The oldest known of these, perhaps, is that 



shown in Fig. 86. Saphaeosaurus from the Jurassic of Solenhofen. 



Its resemblance to the modern 



tuatera is great, and doubtless its 

 habits were very similar, though its 

 rather long tail and rather short neck 

 possibly indicate subaquatic habits. 



CHORISTODERA 



Among the many reptiles of the 

 past which have sought a more con- 

 genial or a safer home in the water 

 „^ qr 1:==^- . few have had a more interesting his- 

 ^^^r '^ t tory, or a briefer one, than those to 



which the late Professor Cope gave 

 the name Choristodera in 1876. 

 Many students of repute consider the 

 group an order, others a suborder 

 of the Rhynchocephalia. The group, 

 whether order or suborder, are inter- 

 esting because of their long and 

 devious migrations from western 

 North America to Europe, or vice 

 versa, through rivers and ponds; 

 interesting also because of the per- 

 sistence of certain old-fashioned traits 

 that clung to them long after their 

 disappearance in other animals. 

 Perhaps these traits were among the 

 causes of their merely moderate success as animals of the water, 

 traits that led to their early dissolution. Like the proganosaurs, 

 which they must have resembled in external appearance not 

 a little, they wandered from their birthplace in the western 

 continent, to perish in the eastern; and like them their span of 

 existence was short. 



Fig. 86. — Sa p/icosaurus , an 

 Upper Jurassic rhynchocephalian. 

 (After Lortet.) 



